Miniature precision snap action switch with one-piece stressed blade construction



Dec. 10, 1968 w, KRlEGER 3,415,962

MINIATURE PRECISION SNAP ACTION SWITCH WITH ONE-PIECE STRESSED BLADE CONSTRUCTION Filed Dec. 9. 1966 5 Sheets-Sheet l A. w. IEGER 3,415,962

MINIATURE PR SION P ACTION SWITCH WITH ONE-PIECE RESSED BLADE GONSTRUCT Filed Dec. 9, 1966 Sheets-Sheet 2 Dec. 10, 1968 (X owl; me ma q LJ a 0%" w fi 16: 2%. l W

Dec. 10, 1968 A. w. KRIEGER 3,415,962

MINIATURE PRECISION SNAP ACTION SWITCH WITH 66 ONE-PIECE STRESSED BLADE CONSTRUCTION Filed Dec. 9, l9 heats-Sheet 5 I muvlor w'afrk t eiwbmcg United States Patent 3,415,962 MINIATURE PRECISION SNAP ACTION SWITCH WITH ONE-PIECE STRESSED BLADE CONSTRUCTION Alvin W. Krieger, Milwaukee, Wis., assignor to Cutler- Hamnrer, Inc., Milwaukee, Wis., a corporation of Delaware Filed Dec. 9, 1966, Ser. No. 600,609 8 Claims. (Cl. 200-67) ABSTRACT OF THE DISCLOSURE A miniature precision snap-action switch having a onepiece snap-action contactor blade removably mounted on a terminal strip support within an insulating housing and including first and second compression force spring strips integral therewith, the first compression force spring strip extending from a point near the contact element which is at one end to a pivot point on said support to apply a force in one direction, and the other compression force spring strip extending with a reentrant bend from the extreme other end thereof to another pivot point on said support for free pivoting thereon the bent end being movable by a plunger to cause switching action.

This invention relates to miniature precision snap action switches and more particularly to switches having a small size and being capable of detecting a small amount of motion and responding thereto to operate with a snap action.

While not limited thereto, the invention is especially applicable to miniature and sub-miniature snap action switches of the self-enclosed, plunger actuated type.

An object of the invention is to provide an improved miniature precision snap action switch.

A more specific object of the invention is to provide a switch of the aforementioned type with improved means affording improved operation and reduction in cost due to fewer parts.

Another specific object of the invention is to provide a snap action switch of the aformentioned type with improved means affording the contact actuator much more overtravel in a switch having smaller overall dimensions.

Another specific object of the invention is to provide a snap action switch of the aforementioned type with,

improved means affording less variation in operating characteristics between switches because the effect of dimensional tolerances is minimized.

Another specific object of the invention is to provide a snap action switch of the aforementioned type with means affording improved contact pressure operating force and mechanical life.

Other objects and advantages of the invention will hereinafter appear.

These and other objects and advantages of the invention and the manner of obtaining them will best be understood by reference to the following description of an embodiment of a miniature precision snap action switch taken in conjunction with the accompanying drawings, wherein:

FIGURE 1 is an isometric view of a miniature precision snap action switch constructed in accordance with the invention;

FIG. 2 is an enlarged front elevational view of the switch of FIG. 1 with the cover removed to show the switch mechanism mounted within the enclosing case, this switch mechanism being shown in its normal off position;

FIG. 3 is a front elevational view like FIG. 2 with 3,415,962 Patented Dec. 10, 1968 the plunger being shown depressed sufficiently to having actuated the switch to its operated or on position;

FIG. 4 is a front elevational view like FIG. 3 with the plunger being shown depressed further to show the amount of overtravel that is possible;

FIG. 5 is a cross-sectional view taken along line 5-5 of FIG. 2;

FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 2;

FIG. 7 is a cross-sectional view taken along line 7-7 of FIG. 2;

FIG. 8 is a front elevational view of the switch blade assembly showing how it would appear in unassembled and unstressed condition; and

FIG. 9 is a bottom view of the switch blade assembly of FIG. 8.

Referring to FIG. 1, there is shown the external appearance of a miniature precision snap action switch constructed in accordance with the invention. As shown therein, the switch is provided with an electrically insulating enclosure comprising a base 2 and a cover 4. Base 2 provides the rear wall and integrally molded therewith most of the upper and lower and left and right walls of the enclosure. Cover 4 provides the front wall and a small part of the upper, lower, left and right walls of the enclosure.

Base 2 is provided with means for supporting a switch operating plunger 6. This means comprises a rectangular aperture 2a extending down through the left-hand portion of the upper wall of the base. This aperture is in the form of a notch in that it communicates with the forward edge of such upper wall to enable the plunger to be dropped thereinto before the cover is riveted onto the base. In this manner, the cover is arranged to form one wall of the aperture and the base forms the other walls of this aperture whereby the plunger is slidably guided for longitudinal movement.

Base 2 is provided with means for pivotally supporting a so-called integral actuator for operating the plunger. This means comprises a cover rivet 8 and an external recess 2b in the upper wall of the base located slightly to the right of the midportion of the base and surrounding the rivet through a portion of its length. As more clearly shown in FIG. 2, this recess provides space around the rivet for an actuator which may be a metal strap bent to provide an offset hook on one end. This hook would retain the strap on rivet 8 allowing the limited pivotal movement and the straight end of such strap would rest on the end of the plunger 6 whereby depression of any portion of the strap would depress the plunger. As actuators of this type have been known heretofore, it has not been illustrated herein but has been described briefly to show the purpose of the recess in the base. As shown in FIG. 1, recess 2b extends from the forward edge of the upper wall of the base toward the rear a sufficient distance to center it on the enclosure when the cover is riveted in place. A second rivet 10 extends through the cover and the right-hand portion of the lower wall of the base to rigidly secure the cover.

The base and cover are provided with complementary interfitting portions to register the cover on the base. For this purpose, the lower left and upper right corners of the cover are notched away and the corresponding corners of the base have forward projections 20 and 2d, respectively, fitting into the notches in the cover. These projections have horizontal mounting holes 22 and 2f therethrough with one of these holes such as 2e being oblong to avoid close tolerance requirements in the locations of the bolts or rivets that are used to secure the switch in place.

As shown in FIG. 2, the switch is of the single pole double throw type whereby a common external terminal may be connected to either one of two selected external terminals. For this purpose, base 2 is provided with a pair of spaced slots 2g in the right wall communicating with the forward edge thereof for receiving a pair of fiat contacts 12 and 14. These contacts are provided at their internal ends with lateral ears 12a and 14a which fit into complementary recesses in the rear wall of the base and in the cover rigidly to secure the contacts in place when the cover is assembled. Suitable contact elements 12b and 14b of low resistance metal are welded on the internal ends of the contacts on the surfaces facing one another. The external ends of these two contacts are provided with suitable terminal connectors such as screws 12c and 14c for connecting the switch to an external circuit.

A common terminal 16 is arranged to receive an improved snap action contactor 18. This common terminal is bent at a right angle at three spaced apart points along its length to provide four functional portions including an external terminal portion 16a arranged horizontally beneath the base and having a suitable connector thereon such as a screw 16b. The adjacent portion 160 extends vertically through a slot 2h in the lower wall of the base. The next portion 16d extends in the left-hand direction within the base and the final portion 16c extends vertically from portion 16d. As shown in FIGS. 2 and 5, common terminal 16 is divided or has its center removed throughout portions 16a and 16d and into the upper part of vertical portion 16c to provide space for contactor 18. Also, upper divided portion 16e has lateral extensions as shown in FIGS. '2 and 6 which continue into the left-hand part of divided portion 16d. These lateral extensions fit into complementary recesses in the rear wall of the base and the cover rigidly to secure the common terminal in the enclosure.

The switch is provided with a one-piece snap action contactor 18 for electrically connecting the common terminal to either one of the selected contacts 12 and 14. This contactor comprises a leaf spring as shown in FIGS. 8 and 9 having contact elements 18a and 18b of low resistance metal secured to upper and lower surfaces at its relatively wide right-hand end for engaging the contact elements of the selected contacts. Contact elements 18a and 18b may form parts of a single rivet swaged in a hole in the leaf spring. For this purpose, this right-hand end of the contactor extends between the internal ends of the selected contacts 12 and 14. A pair of leaf spring compression elements 180 extend in the left-hand direction at a small upward angle from this right-hand end of the contact and are separated by a center strip 18d. These compression elements and center strips are of substantially equal width and are spaced from one another by a pair of narrow gaps to allow freedom of relative movement. This center strip is longer than the compression elements and its left-hand end portion is bent back parallel under neath to underlap the compression elements through a substantial portion of their length. Also, this bent back portion 18e has diverging sides or widens from the bent back point which is some distance to the left of the compression elements 180 toward its end. As shown in FIG. 9, this portion 18e widens starting from or just before the bent back point so that it reaches the full width of the snap action contactor a short distance before its end. This full width is the width of the contactor at the contact elements and at the compression elements. The extreme end of the bent back, widened portion is provided with a short central tongue 18 for retaining this end in the bottom of the U-shaped slot which preventing side movement of the contactor blade. The operating force of the contactor may be selected by making this U-shaped slot the desired depth down into portion 16c.

When the snap action contactor is assembled on the divides the upper end of the common terminal 16 and for common terminal, elements 180 and bent back portion 18c become compression elements. The left ends of compression elements 180 are pivotally supported in the right angle corner pivot P between portions 16d and 16a of the common terminal and are bowed upwardly. Also, the right end of the bent back portion 182 is pivotally supported at the upper end of portion 160 with its tongue 18 confined in the bottom of the U-shaped cutout in such upper end. This causes bent back portion 18a to be bowed downwardly whereby the bent end of center strip 18a! is biased upwardly against the enlarged and rounded lower end 6a of the plunger. Center strip 18d of the contactor is in tension.

In its normal position as shown in FIG. 2, the compression elements bias the bent left end of the contactor upwardly against the plunger. With the plunger in its upper position, the line of action of the contactor blade assembly 18 from the point engaging the plunger to the point of connection of compression elements 18c thereto is above the pivot point P of compression elements 180 at their left ends. Consequently, contact element 18a of the contactor blade assembly is biased against contact element 12b of the upper stationary contact with sufficient contact pressure to make a good electrical connection.

Now when the plunger is depressed to move the bent left end of the contactor blade assembly downward, the contactor will snap from the upper stationary contact to the lower stationary contact. To this end, a point will be reached in the downward movement of the plunger wherein the line of action of the movable contactor passes from above pivot P below such pivot. The line of action of the movable contactor may be defined as a straight line from the point where the left end thereof engages the plunger to the point where both of the compression elements 18c connect with the contactor blade assembly near contact elements 18a and 18b. As this line of action passes just below pivot P, the right end of the contactor will move with a snap action from the upper to the lower stationary contact as shown in FIG. 3.

A characteristic feature of the invention is that the improved structure therein provides much more overtravel for the plunger than is obtained in heretofore known switches of similar type. As will be apparent, after the switch has been operated as shown in FIG. 3, the plunger can be depressed further all of the way in to the position shown in FIG. 4 without affecting the switch position. When the plunger is pressed all the way in, the enlarged lower end thereof stops against ledges 2i shown in FIG. 7 so that bent back portion 182 of the contactor does not engage the base. The advantages of this large amount of overtravel are apparent in that it avoids the necessity of close manufacturing or operating tolerances in the operators which depress the plunger. This large amount of overtravel is obtained by the one-piece construction of contactor blade assembly wherein bent back portion 186 is alsomade as a compression element in addition to compression element 180. When made as a compression element integral with and as a bent back continuation of the fiat leaf spring, portion 182 will bow the proper amount when the plunger is depressed and this portion 18e is thin enough as constructed to clear the hump above hole 2e in the base molding. This is in sharp contrast to prior devices wherein a stiff member, helical compression spring or the like has been used at this point which bottoms on the base before the plunger has been fully depressed. Flexing of bent back portion 18c reduces wipe of the contacts and thus prevents excessive mechanical wear thereof.

Another characteristic feature of the invention is that the one-piece contactor blade construction minimizes the effect of dimensional tolerances thereby affording less variation in operating characteristics between a multiplicity of manufactured switches. To this end, it will be apparent that some of the compressive force is afforded by bent back compression element 18c so that so much less compressive force is required of compression elements 180. In effect, the compressive force is divided between two parts whereby variation in each has correspondingly less effect on operating characteristics.

A further characteristic feature of the invention is the provision of improved contact pressure operating force and longer mechanical life obtained from the one-piece contactor blade construction having the compressive force divided into two parts. It will readily be apparent that division of the compressive force into two parts reduces the flexing in" each compression element 18c and 18e whereby to improve the mechanical life of the switch. This division also provides better control of stress in the upper arch 18g whereby to improve the contact pressure operating force and to make it more consistent.

When the plunger is released, the switch will automatically return to its normal position. Referring to FIG. 4, it will be seen that the left end of the contactor blade applies an upward force on the plunger. Therefore, when the plunger is released, the contactor blade will push it upwardly. This; causes the line of action of the contactor blade to pass from below pivot P above this pivot, causing compression elements 180 to snap contact element 18b away from contact element 14b and to snap contact element 18a into engagement with contact element 1211.

While the apparatus hereinbefore described is effectively adapted to fulfill the objects stated, it is to be understood that I do not intend to confine my invention to the particular preferred embodiment of miniature precision snap action switch disclosed, inasmuch as it is susceptible of various modifications without departing from the scope of the appended claims.

I claim:

1. In a miniature precision snap-action switch having an insulating housing including an insulating plunger extending into the housing and at least two conductive members within the housing and extending to the exterior thereof, one of said members including a stationary contact and the other of said members including supporting means for a movable contactor;

a onepiece snap-action contactor device removably mounted on said supporting means and including a contact element in overlying relation to but separated a short distance from the stationary contact comprising:

an elongated unitary member extending past said sup porting means and having said contact element secured thereto at one end and including;

first compression force means integral with said unitary member and extending from a point near said contact element to a pivot point on said supporting means for applying a force in one direction;

second compression force means which is an integral part of said unitary member and extending with a reentrant bend from the extreme other end thereof to another pivot point on said supporting means on which it is freely, articulately and separably pivoted for applying a force in the opposite direction;

the other end portion of said unitary member being movable by the plunger to cause switching action between said contact element and said stationary contact;

and said other pivot point being spaced fro-m the first mentioned pivot point to cause said unitary member to apply a force also in the outward direction of the plunger in both the normal and operated positions of the contacts. a

2. In a miniature precision snap-action switch having an insulating housing including an insulating plunger extending into the housing and at least two conductive members within the housing and extending to the exterior thereof, one of said members including a stationary contact and the other of said members including supporting means for a movable contactor;

a snap-action contactor device mounted on said supporting means and including a contact element in overlying relation to but separated a short distance from the stationary contact comprising;

an elongated unitary member extending past said supporting means and having said contact element secured thereto atone end and including;

first compression force means integral with said unitary member and extending from a point near said con tact element to a pivot point on said supporting means for applying a force in one direction;

second compression force means integral with said unitary member and extending from the other end thereof to another pivot point on said supporting means for applying a force in the opposite direction; J

said other end of said unitary member bearing against the plunger;

and said other pivot point being spaced from the first mentioned pivot point to cause said unitary member to apply a force also in the outward direction of the plunger in both the normal and operated positions of the contacts;

said first and second compression force means comprising, respectively;

a pair of leaf springs cut for the opposite sides of said elongated unitary member and bent at the connecting point to a small angle so that they are bowed upwardly when their free ends are inserted in the first mentioned pivot point on the supporting means;

and a single leaf spring bent back from the other end of said elongated unitary member so that it is bowed downwardly when its free end is inserted in said other pivot point on the supporting means.

3. The invention defined in claim 1 wherein:

the pivot point of said bent back second compression force means is offset vertically and horizontally on the supporting means from the pivot point of said first compression force means.

4. The invention defined in claim 5 wherein:

the horizontal offset of said pivot points affords overlapping of said bent back second compression force means and said first compression force means a substantial amount thereby to provide a large amount of overtravel for the plunger after it has been depressed enoughto cause snap action closure of said contact element against said stationary contact.

5. In a miniature precision snap-action switch having an insulating housing including an insulating plunger ex? tending into the housing and at least two conductive members within the housing and extending to the exterior thereof, one of said members including a stationary contact and the other of said members including supporting means for a movable contactor;

a snap-action contactor device mounted on said supporting means and including a contact element in overlying relation to but separated a short distance from the stationary contact comprising;

an elongated unitary member extending past said supporting means and having said contact element secured thereto at one end and including;

first compression force means integral with said unitary member and extending from a point near said contact element to a pivot point on said supporting means for applying a force in one direction;

second compression force means integral with said unitary member and extending from the other end thereof to another pivot point on said supporting means for applying a force in the opposite direction;

said other end of said unitary member bearing against the plunger;

and said other pivot point being spaced from the first mentioned pivot point to cause said unitary member to apply a force also in the outward direction of the plunger in both the normal and operated positions of the contacts;

said elongated unitary member and said first and second compression force means comprising;

a one piece leaf spring member including an elongated central leaf spring having a pair of lateral leaf springs extending from one end thereof therealong with an upward bow with their free ends in said first pivot point to form said first compression force means and the other end of said central leaf spring having been bent back therebelow and having a downward bow with its free end in said second pivot point and underlapping a substantial portion of said pair of lateral leaf springs thereby to afford a large amount of overtravel to the plunger engaging said central leaf spring at its bent end.

6. The invention defined in claim 1, together with:

an enlarged end on the plunger within the housing;

and at least one ledge within the housing against which said enlarged end stops when said plunger is fully depressed to prevent any portion of said snap-action contactor device from being damaged against the housing.

7. The invention defined in claim 1, wherein the supporting means comprises:

a metal strap having a center strip cut out for a predetermined distance from the end thereof within the housing to provide parallel strips with space therebetween through which said elongated unitary member extends;

said parallel strips having two spaced apart right angle bends in opposite directions to provide two portions parallel but offset from one another;

the acute angle formed by one of said bends forming a pivot for said first compression force means;

References Cited UNITED STATES PATENTS 2,740,857 4/1956 Porland. 2,980,774- 4/1961 Millerwise. 3,142,741 7/ 1964 Bury. 3,248,959 5/1966 Angold. 1,960,020 5/ 1934 McGall. 2,486,033 10 1949 Kaminky. 2,565,790 8/ 1951 Van Ryan et al. 3,170,998 2/ 1965 Stahl.

FOREIGN PATENTS 609,680 10/ 1948 Great Britain.

1,358,588 3/1964 France.

OTHER REFERENCES Wintzer, Ger., Appl. No. 1,118,310, pub. 11-61, 3 Shts., dwgs.

ROBERT K. SCHAEFER, Primary Examiner.

D. SMITH, JR., Assistant Examin r. 

